Death of a Soldier - ID for murderer please

Observation - Death of a Soldier - ID for murderer please - Global. Description: Found this fly chomping through a Soldier Beetle at lunchtime. This did not cool the ardour of other Soldier Beetles on the same Hogweed. But what is the murderer's name please?
(Text revised to reflect Chris' correction!)

Found this fly chomping through a Soldier Beetle at lunchtime. This did not cool the ardour of other Soldier Beetles on the same Hogweed. But what is the murderer's name please?